This disclosure relates to an impingement cooling device for use in a system in need of component cooling, for example, a thermal spray coating process.
Some aircraft components, such as burner liners, are thermally sprayed with a polymer containing ceramic and metallic materials to improve the thermal properties of the component. Burner liners, for example, have an annular outer surface and an annular inner surface that are thermally coated. The conditions during coating application must be tightly controlled to achieve desired thermal coating deposition. To provide a uniform thermal coating on the outer surface, the burner liner is rotated at a predetermined speed on a table and the spray torch is moved vertically at an indexing rate. Additionally, the spray torch's distance from the component, the plasma conditions, and material feed rate are controlled during deposition. The temperature of the component must also be controlled to avoid an undesired porosity level in the thermal coating and maintain desired deposition efficiency. The component temperature also affects the other thermal coating parameters.
One type of ceramic coating process uses an air plasma spray that produces significant heat in the component being coated. A typical coating process must accommodate components of various sizes. As a result, smaller diameter parts become hotter than larger diameter parts. The difference in temperature between different sized components thermally coated on the same machine makes selecting the desired thermal coating parameters difficult.
Cooling devices have been employed to control the temperature, but they have not been able to do so consistently. For example, one cooling setup has employed low velocity, high volume air nozzles, which are separate and discrete from one another, that are directed at the component surface. Air is supplied at a regulated pressure of about 45 psi (310 kPa), to achieve the desired high air flow rate of about 750 standard cubic feet per hour (scfh) (21 kilo liters per hour). The nozzle openings used were one-eighth inch (3.2 mm), and arranged parallel to and in close proximity to the spray plume at a distance of about 2.5 inches (63.5 mm) from the coating surface. Additionally, air amplifier blowers were used to generate a high flow rate of cooling air by entraining up to about ten times the flow rate of ambient air into about 3600 scfh (102 kL/h) each of compressed air supplied at about 80 psi (552 kPa). The air amplifier blowers were arranged between two and twelve inches from the component surface and provided a cooling air stream that was about two inches in diameter (51 mm). This cooling device arrangement was very sensitive to slight changes in thermal coating parameters, making thermal coating results erratic.
What is needed is a cooling device that uses less air while yielding more consistent results in the thermal coating.